Movable panels or covers, such as hoods and trunk lids, are typically attached to the body or frame of a motor vehicle by means of one or more hinges, pins, or other type of revolute joint. Such movable panels or covers provide easy access to otherwise covered and hidden parts of the vehicle, such as the engine and trunk. The panels may possess considerable weight. For example, the hood of a large truck may exceed 100 pounds. Significant effort may be required to open or close a heavy panel or cover. In addition, a heavy panel or cover may cause injury should it fall open or shut in an uncontrolled manner.
To reduce the effort of opening such panels and reduce the risk of injury, it is often desirable to provide a force about the pivot axis of the hinge to counteract the weight of the panel. Typically the counteracting force is provided by springs which are arranged so that they are operative at the fully opened and closed positions of the vehicle panel. For example, extension springs may be arranged so that they are stretched when the hood of an automobile is fully closed and so that the stretching of the springs creates a force about the pivot axis of the hinge which tends to assist a user in lifting the hood to an open position. Other lift assisting mechanisms may employ arrangements of compression springs, coil springs, gas-springs, torsion-bars and the like.
However, such mechanisms for reducing the effort needed to open or close a vehicle panel require many parts in addition to the parts needed merely to provide the hinged motion. The additional parts add to vehicle weight and complexity and may increase vehicle manufacturing, maintenance, and operating costs. Accordingly, it would be desirable to provide a simple hinged or revolute joint that provides assistance in opening or closing a panel or cover without the need for additional parts.
In addition to the foregoing, it is also often desirable to isolate panels and covers from other parts of the vehicle structure to accommodate relative motion between them. For example, vehicle bodies and frames flex and vibrate as the vehicle is driven over a roadway. Vehicle bodies and frames also bend and flex due to differences in the thermal expansion characteristics of various component parts of the vehicle body or frame. Flexing may cause the mounting points between a movable panel or cover and the vehicle body to move relative to each other. The relative motion of the mounting points may create significant and potentially destructive stresses in the panel. Isolating the panel from the mounting points may reduce the stresses imparted to the panel.
One means of isolating a panel is to provide an elastomeric resilient mount between the panel and mounting point. For example, rubber grommets may be provided around the bolts attaching a panel to a hinge. Such isolation mounts provide for limited motion between the panel and the mounting points. Another means of isolating the panel from the mounting points includes providing cylindrical elastomeric bushings located concentric with the pivot axis of the hinge. Yet another isolation method is to provide an additional hinge joint having an axis substantially aligned with the longitudinal axis of the vehicle. Combinations of these isolation techniques may also be used.
However, such isolation techniques also require many parts in addition to those merely needed to provide for hinged motion of the vehicle panel with respect to the vehicle body or frame. The additional parts also add to vehicle weight and complexity and may increase vehicle manufacturing, maintenance, and operating costs. Accordingly, it would be desirable to provide a hinged or revolute joint that provides isolation between the motion of the body or frame of a motor vehicle and a panel or cover attached to the vehicle.